Presently, the industrial pure aluminum is primarily produced by cryolite-alumina fused salt. A dedicated device usually employed in the above process includes an electrolytic cell of which the inside is lined with carbon materials.
Refractory materials and heat insulating bricks are provided between a steel case and a carbon liner of the electrolytic cell. The carbon liner within the electrolytic cell is generally structured by laying carbon bricks (or blocks) made of anthracites or graphite materials or the compound thereof, which has a better anti-sodium or anti-electrolytic corrosivity. Carbon pastes made in above carbon materials are tamped at a joint between the bricks or blocks. A steel rod is disposed at the bottom of the carbon blocks at the bottom of the electrolytic cell and extended out of the case of the electrolysis cell. Such steel rod is usually referred to a cathode steel rod of the electrolysis cell. A carbon anode made of petroleum coke is suspended above the electrolysis cell. An anode guide rod made in metal is disposed above the anode of the electrolysis cell, through which the current is led in. Molten aluminum and cryolite-alumina electrolyte melt having a temperature between 940-970° C. are provided between the carbon cathode and the carbon anode of the electrolysis cell. The molten aluminum and the electrolyte melt are not fused from each other, and the density of the aluminum is lager than that of the electrolyte melt, thus, the aluminum is contacted with the carbon cathode below the electrolyte melt. When a direct current is led from the carbon anode of the electrolytic cell and led out of the carbon cathode thereof; since the electrolyte melt is an ionic conductor, the cryolite molten with alumina is electrochemically reacted at the cathode and the anode. Accordingly, a reaction that the oxygen produced by the oxygen-carrying ion being discharged on the anode reacts with the carbon on the carbon anode is carried out, and the electrolyte resulting from the reaction in the CO2 form is escaped from the surface of the anode. Aluminum-carrying ion is discharged on the cathode so as to obtain three electrons to generate metal aluminum. This cathode reaction is performed on the surface of the molten aluminum within the electrolytic cell. The inter electrode distance refers to the distance between the cathode surface and the bottom surface of the carbon anode within the electrolytic cell. Typically, in the industrial aluminum electrolytic cell, the inter electrode distance within the electrolytic cell is 4-5 cm. The inter electrode distance generally is a crucial technical parameter in the industrial aluminum electrolytic production, the inter electrode distance with too high or too low value will impose great influence the aluminum electrolytic production.
More specifically, the inter electrode distance with too low value may increase a secondary reaction between the metal aluminum molten from the cathode surface into the electrolytic melt and the anode gas, so that the current efficiency is reduced.
The inter electrode distance with too high value may increase the cell voltage within the electrolytic cell, so that the power consumption for the direct current of the production of the aluminum electrolyzing is increased.
For the production of the aluminum electrolyzing, it is desired that the electrolytic cell has the highest current efficiency and the lowest power consumption, during the aluminum electrolyzing, the power consumption for the direct current can be presented by following formula:W(kilowatt-hour/ton of aluminum)=2980*Va/CE 
Wherein the Va is an average cell voltage (V) within the electrolytic cell, CE is the current efficiency of electrolytic cell (%).
It can be seen from above formula, the goal of reducing the power consumption for aluminum electrolyzing production can be realized by increasing the current efficiency of electrolytic cell and reducing the average cell voltage within the electrolytic cell.
The inter electrode distance of the electrolytic cell is an important process and technical parameter for determining the size of the cell voltage. For the existing conventional industrial electrolytic cell, the cell voltage is reduced about 35-40 mV by reducing 1 mm of inter electrode distance, thus, it can be seen from formula (1), while the current efficiency of electrolytic cell is not reduced, the direct current power consumption for production of the aluminum electrolyzing can reduce over 100 kilowatt-hour per ton of aluminum. Therefore, it can be seen that reducing the inter electrode distance is advantageously benefit for the power consumption for production of the aluminum electrolyzing under the circumstance of the current efficiency not being effected. Typically, the inter electrode distance of industrial aluminum electrolytic cell is about 4.0-5.0 cm, which is measured by bringing out of the cold steel towline from the electrolytic cell after the cold steel towline having a hook sized about 15 mm vertically extended into the electrolyte melt of the electrolytic cell and uprightly hooked on the bottom top lift of the anode in about 1 minute. That is, the distance is the one between the molten aluminum surface and the top lift of the bottom of the anode which is obtained by using the interface between the aluminum and the electrolyte. Obviously, such distance is not the real inter electrode distance of the electrolytic cell because the molten aluminum surface is waved or fluctuated when the molten aluminum surface within the electrolytic cell is undergoing the electromagnetic force within the electrolytic cell or the anode gas is escaped from the anode.
It can be found in the literature that the wave crest height of the molten aluminum surface at the cathode of the electrolytic cell is about 2.0 cm. If the molten aluminum in the electrolytic cell is not waved, the electrolytic cell can perform electrolyzing production when the inter electrode distance is 2.0 to 3.0 cm. Thus, the cell voltage can reduce 0.7-1.0 v, so that the target of saving the power consumption of the electrolytic cell about 2000 to 3000 kilowatt-hour/ton of aluminum can be achieved. Based on such fundamentals, several aerial drainage type TiB2/C cathode electrolytic cells without molten aluminum waved at the cathode have been developed and put into the industrial experiments, the highest current strength of the aerial drainage type TiB2/C cathode electrolytic cell is reached to 70 KA, the cathode current density is reached to 0.99 A.cm−2, and the power consumption is 1280 killowatt-hour/ton of aluminum. However, according to the information obtained from the Sixth International Aluminum Electrolyzing Technique Conference in Australia, such experiment only tests for 70 days. There is no more information about such experiment and applications since the aforesaid experiment 8 years ago.
According to the experiment result for self-heated 1350-2000 A aerial drainage type TiB2/C cathode electrolytic cell supported by China Natural Science Fund, such electrolytic cell has an unexpected defect. That is, the over voltage of the cathode of the aerial drainage type TiB2/C cathode electrolytic cell is too high, i.e., higher than the normal one about 0.5 v. Although the fundamentals and mechanisms of the above phenomena are not quite clear, one reason may be considered. Specifically, as a result of polarization of the cathode, a macromolecule cryolite is formed on the cathode surface, and the macromolecule cryolite is slow in diffusion and mass transport, so that concentration polarization over voltage on the cathode surface is generated. Up to now, there is no solution to solve above problem, so the development and research of such aerial drainage type TiB2/C cathode the electrolytic cell is impeded. An other serious disadvantage of the aerial drainage type TiB2/C cathode electrolytic cell is: there is not enough amount of molten aluminum in the cathode, so that the heat stability of the electrolytic cell is poor, particularly, the huge amount of heat momentarily produced in the electrolytic cell under the anode effect is unable to dissipated through the molten aluminum having good heat conductivity or stored by the molten aluminum.
Moreover, the existing aluminum electrolytic cell is not good in life span; the longest life span for the cathode only has 2500-3000 days. In those disrepaired electrolytic cells, most of them are damaged in the early period, that is, it is caused by, in the early period of the production within the electrolytic cell, the cathode molten aluminum within the cell is leaked to the cell bottom to melt and corrode the cathode steel rod through cracks formed at the bonding portion between the cathode carbon blocks internally lined in the cell bottom and the carbon pastes during burning and producing, or through the crack produced on the carbon blocks body during burning.